Cameron was taken to hospital in Sydney with a suspected left collarbone fracture suffered in the club's 13-point loss to GWS at Engie Stadium on Saturday.
The two-time Coleman Medal winner was in agony after a brutal fourth-quarter collision with Giants midfielder Clayton Oliver.
Depending on the severity of Cameron's injury, the star forward could miss six to eight weeks.
Geelong are eighth (9-8), with six home-and-away rounds remaining.
Cats defender Jack Henry suffered a knock to the throat in the second term, before Tanner Bruhn hurt his neck following a heavy third-quarter tackle from Giants midfielder Toby Bedford.
All three remained in Sydney, with Cats coach Chris Scott unsure on the prognosis.
"(Cameron) was pretty sore, so I'm not sure the extent of it," Scott said.
"I don't pressure our medical staff to keep me in the loop in an acute fashion anyway. That'll sort of play itself out over time."
It is a massive setback for Cameron, who was already battling to find form amid lingering right-arm issues.
The 33-year-old fractured the arm in last year's grand final loss to Brisbane and still wears an arm guard.
After going goalless from four disposals in last week's loss to the reigning premiers, Cameron impressed in defence against the Giants.
He finished with 11 marks, 19 touches and four intercept possessions and started in a match-up against former Giants teammate and podcast co-host Toby Greene.
"Up until then (Cameron's injury), we thought he was very influential," Scott said.
"We'd like him in the forward half as well as the back half, but you've got to choose.
"We felt like we were getting enough of him in the back half to offset the fact he wasn't in our forward half."
GWS coach Adam Kingsley admitted the change took the Giants by surprise.
"It was just a matter of sort of treating him as a back," Kingsley said.
"I heard during the week that they were going to try or might think about trying some things.
"We didn't predict that's where he'd start, but I thought we handled it OK."
Asked if his inside knowledge was from captain Greene, Kingsley joked: "We didn't know. Our intel isn't good enough. Toby needs to do a bit more work."
In an intriguing side-plot, off-contract Greene has been heavily linked with a move to Geelong to reunite with Cameron.
Amid the speculation, Greene stood tall to help the Giants turn around a 39-point deficit, finishing with 33 touches and seven clearances.
"I didn't notice a difference in his demeanour all week, or his preparation, or his leadership, or his training," Kingsley said.
"He's at a high level in all of those spaces every single week, irrespective of who he plays. That's why he's such a great player for us.
"The speculation and all that stuff is going to linger, but to be fair, he has led as well as he ever has in my time here."
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